These devices will transmit contact control and alarm signals over any digital video link. The signal is encoded in the picture area prior to digitizing, so it will pass through all digital video compression systems. Most digital video compression systems block all signals in the vertical interval. This system uses the visual picture area to send contact closure information.

The ATU/ARU-8D will transmit contact control and alarm signals over any digital video link. The signal is encoded in the picture area prior to digitizing, so it will pass through all digital video compression systems. Most digital video compression systems block all signals in the vertical interval. This system uses the visual picture area to send contact closure information.

Contact closures on the ATU-8D input will be repeated as contact closures at the ARU-8D output. This system uses one active picture line to transmit the contact information and it is field programmable from lines 20 to 25.

The ATU-8D ALARM TRANSMITTING UNIT and the ARU-8D ALARM RECEIVING UNIT together make up an 8 channel alarm and control system. The transmitter removes the picture information from the first available active line and then inserts the coded contact information. At the other end of the video link the receiver decodes the contact information and then removes it from the video signal.

A system alarm contact will operate upon loss of power to either terminal or loss of transmission path (video link failure). An internal video sync generator takes over and maintains continuous alarm system operation in the event of video signal failure.